1. Field of Invention
The present invention relates generally to apparatus embedded in and or applied to gasket structures, and particularly to sensing apparatus applied to combustion gaskets of internal combustion engines. More specifically, the invention relates to pressure sensing apparatus provided within structures of MLS combustion gaskets for measuring pressure levels of combustion gases within the cylinder bores of internal combustion engines.
2. Description of the Prior Art
It is known to employ electronic sensors in gaskets for sealing between engine components including, for example, the block and cylinder head of a multi-cylinder internal combustion engine. In one case, the gasket comprises a sealing plate having several combustion chamber orifices, with combustion chamber sealing elements situated on the edges of the sealing plate surrounding the combustion chamber orifices. The gasket includes sensor elements for cylinder-specific detection of sealing movements perpendicular to the plane of the sealing plate, caused by pressure changes in respective combustion chambers being measured. All of the sensor elements are arranged outside of the combustion chamber sealing elements, and can be piezoelectric and piezoresistive, as well as glass fiber light guide-style sensors.
In another example, a gasket enclosed sensor system is employed for measurement of combustion chamber parameters and delivery of signals to points external of the engine. The gasket includes a combustion opening substantially surrounding a combustion chamber, and includes an access opening extending from the combustion chamber to a point external of the engine. A metallic sensor terminal is positioned within the access opening, and insulating material substantially surrounds the metallic sensor terminal.
In yet another example, a fluid sensor and associated circuitry are used to indicate presence of oil flow in a multi-cylinder internal combustion engine. The oil sensor includes a heating element positioned within the oil line, directly in the oil flow path. A comparator measures the value of signals from upstream and downstream heat sensors, and triggers a switching circuit when the temperature at the sensors approach one another to indicate an adequate oil flow to the engine.
In still another example, a gasket formed in the shape of an exhaust flange includes a load sensor comprising a pressure sensitive electrically resistive material positioned between electrodes and conductors extending outwardly of the perimeter of the gasket. A seal provided between first and second layers of the gasket, and about the load sensor, provides a seal for the electrodes, which are positioned in a cavity to protect the sensor from fluids.
A sensor for a multiple layer steel (MLS) cylinder head gasket aperture boundary is adapted to measure combustion pressures occurring in internal combustion engines for detection and control of engine knock, i.e. predetonation conditions, among other purposes. The structure of the sensor includes a pressure sensitive membrane at one end of a metal tube, wherein the tube is positioned adjacent a cylinder bore aperture boundary. The membrane is affixed to the tube at its aperture boundary end, and an optical sensor structure is fixed within the tube downstream of the membrane. The tube protects the optical sensor from becoming damaged under high sealing stresses that occur at the cylinder bore. As disclosed, the sensor is placed into a spacer layer of the MLS gasket, in a groove machined into the spacer layer, and an optical fiber wire coupled with a sensor from each cylinder bore is bundled into a common groove of the spacer layer. The groove may be located outside of the conventional component boundary of the gasket. Thus, the spacer layer may be extended radially outwardly of the conventional component perimeter at the convenience of the gasket designer. Finally, a converter is employed to change optical signals received from the optical wire into electrical signals for appropriate transmittal to a microprocessor of an engine control unit.
Where a plurality of cylinder bores is provided in the gasket, and to the extent that pressure sensing is provided at each bore, a real time quality engine management control opportunity based upon cylinder-by-cylinder measurement of combustion pressure is provided. The specific cylinder-to-cylinder data can be input into an engine control unit module that includes systems for optimization of engine performance parameters, including fuel economy and emissions levels, among others.
As the pressure sensor apparatus is designed to be applied to a protective tube positioned in a groove of a spacer layer, the apparatus may be positioned between beaded or active layers of a multiple-layered steel gasket without severe risk of being crushed or overstressed. Moreover, the sensor may be positioned relatively close to the flame front within the gasket structure, and as such can be particularly effective to measure pressure levels of cylinder-specific combustion gases in real time.